In November 1941, with World War II nearly two years underway, the Coast Guard was transferred from the U.S. Treasury Department to the U.S. Navy.

Germany declared war on the U.S. on 11 December 1941, and Icarus was rearmed and assigned to the Eastern Sea Frontier for patrol duty off the East Coast.

Icarus anticipated the presumed U-boat's next move and dropped 5 depth charges at the site of the prior torpedo explosion.

When the U-boat's crew abandoned ship, Icarus ceased fire, releasing one last depth charge over U-352 as it sank beneath the water.

[8] Rearmed at Norfolk Navy Yard, Icarus resumed her duties as a convoy escort, anti-submarine patroller and search and rescue ship.